It is known to win mineral underground with the use of a longwall conveyor installed alongside the mineral face along which a winning machine is guided for movement back and forth along the face. The conveyor then transports material stripped from the face away from the working. After the passage of the winning machine the conveyor is advanced in sections up towards the face into the winning lane which has been created by stripping mineral from the face with the machine by operating hydraulic shifting rams coupled to the individual channel sections of the conveyor and engaging on roof supports which serve as abutments for the shifting forces. In known control methods, after the passage of the winning machine, the conveyor is `snaked` up to the material face by charging a plurality of shifting rams with pressure fluid. The shifting rams are either actuated individually in succession by an operator and kept under pressure until the conveyor shifts up to the face or else they are combined into so-called `bank-push` groups wherein the rams of one of these groups are all actuated in unison. After the conveyor has been shifted the rams are disconnected, usually in response to an operator initiated command. If the advancing forces provided by the rams is not sufficient to advance the conveyor by the desired distance, for example, because the conveyor channel sections are pushed against a ridge or step in the floor of the working, a further bank-push group is connected and the rams of the preceding bank-push are maintained under pressure until the conveyor has been advanced. In practice, it often occurs that in trying to overcome an obstacle, for example, the ridge or step mentioned above, all or at least some of the actuated rams extend out at the same time. This tends to overload the hydraulic fluid supply system and can lead to serious problems. There is a need to develop an improved method which loads the conveyor as little as possible by carefully controlling the forces imparted by the shifting rams and which avoids overloading the hydraulic supply system.